Economically-, environmentally-, and socially-sustainable approaches to agriculture and food production are required to meet the needs of a growing global population. By 2050 the United Nations' Food and Agriculture Organization projects that total food production must increase by 70% to meet the needs of the growing population, a challenge that is exacerbated by numerous factors, including diminishing freshwater resources, increasing competition for arable land, rising energy prices, increasing input costs, and the likely need for crops to adapt to the pressures of a drier, hotter, and more extreme global climate. The need to grow nearly twice as much food with less water in more arid climates is driving a critical need for innovations in crop water use efficiency and temperature tolerance.
Today, crop performance is optimized primarily via technologies directed towards the interplay between crop genotype (e.g., plant breeding, genetically-modified (GM) crops) and its surrounding environment (e.g., fertilizer, synthetic herbicides, pesticides). While these paradigms have assisted in doubling global food production in the past fifty years, yield growth rates have stalled in many major crops, and shifts in the climate have been linked to production instability and declines in important crops such as wheat, driving an urgent need for novel solutions to crop yield improvement. In addition to their long development and regulatory timelines, public fears of GM-crops and synthetic chemicals has challenged their use in many key crops and countries, resulting in a complete lack of acceptance for GM traits in wheat and the exclusion of GM crops and many synthetic chemistries from European markets. Thus, there is a significant need for innovative, effective, environmentally-sustainable, and publically-acceptable approaches to improving the yield and resilience of crops to severe drought and heat stresses.
Improvement of crop resilience to heat and drought stress has proven challenging for conventional genetic and chemical paradigms for crop improvement. This challenge is in part due to the complex, network-level changes that arise during exposure to these stresses. For example, plants under such stress can succumb to a variety of physiological and developmental damages, including dehydration, elevated reactive oxygen species, impairment of photosynthetic carbon assimilation, inhibition of translocation of assimilates, increased respiration, reduced organ size due to a decrease in the duration of developmental phases, disruption of seed development, and a reduction in fertility.
Like humans, who utilize a complement of beneficial microbial symbionts, plants have been purported to derive a benefit from the vast array of bacteria and fungi that live both within and around their tissues in order to support the plant's health and growth. As described in detail herein, endophytes are fungal or bacterial organisms that live within plants. Bacterial endophytes, such as Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes, and Verrucomicrobia, appear to inhabit various host plant tissues and have been isolated from plant leaves, stems, and roots.
To date, a small number of these symbiotic endophyte-host relationships have been analyzed in limited studies to provide fitness benefits to model host plants within controlled laboratory settings, such as enhancement of biomass production (i.e., yield) and nutrition, increased tolerance to stress such as drought and pests. Yet, such endophytes have been demonstrated to be ineffective or of limited efficacy in conferring benefits to a variety of agriculturally-important plants such as modern cereals; as such, they do not adequately address the need to provide improved yield and tolerance to environmental stresses present in many agricultural situations for such crops, particularly drought and heat.
Thus, there is a need for compositions and methods of providing cereal crops with improved yield and resistance to various environmental stresses. Provided herein are novel compositions of symbionts, bacterial and fungal endophytes, as well as novel symbiont-plant compositions, created based on the analysis of the key properties that enhance the utility and commercialization of an endophytic composition.